Preclinical models of tumors have the potential to become valuable tools for commercial drug research and development, and 3D culture systems are gaining attraction in this area, including prostate cancer (PCa) research. However, nearly all 3D drug design and screening assessments are based on 2D experiments, indicating the limitations of 3D drug testing. To simulate the natural response of human cells to the drug, we detected the half-maximal inhibitory concentration (IC50) changes of 2D/3D LNCaP cells to the drug docetaxel and the sensitivity of different morphologies of 2D/3D LNCaP to docetaxel treatment. In contrast to 2D LNCaP cells, the evaluation of the susceptibility of LNCaP spheroids to treatment was more complicated. The fitness of IC50 curves of 2D and 3D tumor cell preclinical models differed significantly. IC50curves were unsuitable for large LNCaP spheroids. More evaluation indexes (e.g., maximal inhibition) and experiments (e.g., spheroids formation) should be explored and performed to systematically evaluate the susceptibility.